Concealed hinge



Oct. 25, 1955 c. MACKINTOSH CONCEALED HINGE 5 Sheets-Sheet 1 Filed March17, 1952 INVENTOR ATTORNEYS Oct. 25, 1955 Filed March 17, 1952 c.MACKINTOSH 2,721,353

CONCEALED HINGE 5 SheetsSheet 2 7; I N VENTOR MEM BY 96% an M ATTORNEYOct. 25, 1955 Q MACK|NTQSH 2,721,353

CONCEALED HINGE Filed March 17. 1952 s Sheets-Sheet a INVENTOR M7 MWATTORNEY Get. 25, 1955 c, MAcKlNTCsH 2,721,353

CONCEALED HINGE 1N VENTOR ATTORNEYS Oct. 25, 1-955 c. MACKINTOSHCONCEALED HINGE 5 Sheets-Sheet 5 Filed March 17, 1952 INVENTOR y M; ydfia u/ ATTORNEYS United States Patent CONCEALED HINGE CharlesMackintosh, Los Angeles, Calif.

Application March 17, 1952, Serial No. 277,051

11 Claims. (Cl. 16 -164) This invention relates to hinges and moreparticularly to concealed hinged of the multiple linkage type for doorsor other closures.

The general object of the invention is the provision of new and improvedhinges of the type described; which are sturdy and strong and capable ofsupporting doors or closures of considerable weight; which are compactin construction and arrangement whereby they may be housed withincomparatively shallow recesses in the relatively movable swingingmembers; and which may be easily and economically manufactured andinstalled.

The novel hinges are especially useful in connection with doors or heavyclosures which are adapted to be hung vertically and swung in thehorizontal direction.

Other features which contribute to the attainment of the objects of theinvention include the provision of concealed hinges with multiplelinkages connecting the leaves, which linkages are adapted to be stackedin vertical planes in both the closed position of the closure and theposition in which the closure and support have been swung relatively toeach other from said closed position through an angle of 180. Also, inthe preferred embodiments of the invention, the construction is suchthat the pintle pins sustain practically no tension or shearingstresses, but the door-supporting stresses are resolved into compressionbearing stresses between the superposed linkages, the pins merelyserving to guide the movements of the linkage and the door andpreventing the door from falling away from its proper erect position.

The invention also contemplates the provision of resilient means forurging the hinge mechanism away from dead center at its 180 openposition, when it is desired to close the door.

Other objects and features of novelty will be apparent from thefollowing specification when read in connection with the accompanyingdrawings in which certain embodiments of the invention are illustratedby way of example.

In the drawings:

Figure 1 is a fragmentary view in transverse section through portions ofa door or other closure and a jamb with which it is associated, andshowing somewhat diagrammatically a hinge embodying the principles ofthe invention, the door being in closed position in alignment with thejamb;

Figure 2 is a similar view showing in solid lines the position of thehinge when the door is fully opened at an angle of 180 with respect tothe jamb, and indicating in broken lines the position of the door at 90or half open;

Figure 3 is a vertical sectional view taken on line 3-3 of Figure l, andshowing one of the two hinge leaves and the linkage system in elevation,as they appear in doorclosed position;

Figure 4 is a vertical sectional view taken on line 4-4 of Figures 1 and3;

Figure 5 is a view in elevation of the hinge installation when the dooris in the wide open position shown in full lines in Figure 2;

Figure 6 is a fragmentary perspective view of the novel multiple linkagearrangement of the hinge assembly, in door-closed position;

Figures 7 and 8 are views in perspective of the two hinge plates, one ofwhich is fastened to the edge of the door and the other to the jamb;

Figures 9 and 10 are perspective views of certain connecting linksadapted to be pivotally attached to the projecting ears or lugs of thehinge plates or leaves;

Figure 11 is a view in perspective of a binding cleat or bar forstrengthening and rigidifying the hinge linkage structure, and providinga fulcrum agent for the levering actions of the various linkages;

Figure 12 is a view in elevation of one of the resilient plugs or rubberspring elements which serve to urge the linkage assembly away from deadcenter when the door is in open position;

Figure 13 is a fragmentary vertical sectional view through a linkageconnection showing a drive-pin pintle which may be employed in any orall of the embodiments illustrated instead of the screw or bolt pintlessuch as shown in Figures 4, 5 and 6;

Figures 14 and 15 are side and end views respectively of one type ofdrive-pin used;

Figure 16 is a fragmentary transverse sectional view through theadjacent portions of a door and a jamb illustrating another form ofhinge included within the broad scope of the present invention, theclosed position of the parts being illustrated in solid lines, and apartly open and a fully open position being indicated by broken lines;

Figure 17 is a view in elevation of a jamb plate forming a part of thehinge;

Figure 18 is an edge view of the same plate;

Figure 19 is a view in vertical section taken on line 19-19 of Figure16;

Figure 20 is a view in elevation of the adjoining portions of the doorand jamb in wide open position, and showing very clearly the positionsof the various linkages of the hinge assembly; and

Figures 21 and 22 are perspective views respectively of two of theconnecting links employed.

The embodiment of the invention illustrated in Figures 1-15 of thedrawings will now be described in detail. Probably the best approach toan understanding of this construction will be through an examination ofFigures 5, 7, and 8 of the drawings. The door element which representsgenerally the closure of the hinged system is designated in thesefigures by the reference character D, and the supporting member or jambis designated J. Each hinge assembly or installation comprises twoleaves or plates one of which is secured within a recess 10 within theedge portion of the jamb J and the other within a similar recess 11within the edge of the door D. The jamb plate or leaf is designated JPand the plate or leaf which is secured to the door is designated DP.Suitable fastening means such as screws may pass through the openings 12in these plates to secure them to the jamb and door edges. In thepreferred con struction, the appropriately designated plates are securedto the corresponding elements of the closure arrangement, but undercertain circumstances, it would be possible to reverse the plates withrespect to the jamb and door elements.

The jamb leaf JP shown in Figure 8 of the drawings is of rectangularconfiguration and is provided with an elongated longitudinally extendingslot S for a purpose which will be described presently. At spaced pointsalong the inner margin of the leaf JP lugs or cars J1 and J3 are struckfrom the plate and bent outwardly as clearly shown in Figure 8. Theselugs are provided with vertical openings 15 through which pintleelements may be passed as described in connection with other figures.Another pair of lugs J2 and J4 are struck from the plate JP at theleft-hand margin of the slot S as viewed in Figure 8. These lugs or earsalso have pintle receiving openings 15 provided therein. The plate IP isalso provided near its inner or left-hand margin with recesses orsockets l9 and 2th for the reception of certain resilient elements orplugs to be described later.

The door leaf DP is also provided with inner marginal ears which arestruck from the face of the plate and these ears are designated D1 andD3. Other staggered lugs are struck from the intermediate portion of theplate DP as indicated at D2 and D4 in Figure 7. These lugs are alsoprovided with pintle receiving openings 15. Spring plug receivingsockets 21 and 22 are also provided to the plate or leaf DP.

Referring now more particularly to Figures 5 ,9, l0, and ll of thedrawings, it will be seen that a vertical series of links are providedfor connecting and supporting the closure and jamb members and theselinks are of two general configurations, as shown respectively inFigures 9 and 10, the shapes of the link elements making them readilyadapted to be economically manufactured by extrusion processes. Thelinks are designated in order of their occurrence from top to bottom ofthe assembly as follows: L1, L2, L3, L4, L11, L22, L33, L44. The linksL1, L2, L11 and L22 are of the construction and configuration shown inFigure 9 in which three bosses 25, 2-6, and 27 are formed on each linkand each boss provided with pintle receiving openings 30. The links L3,L4, L33 and L44, shown in Figure 10, are of almost twice the height ofthe links illustrated in Figure 9 and one end of each of these links isnotched out as at $2 to approximately halve the height of the link atthat end. The links shown in Figure 16 are provided with bosses 35, 36,and 37 and each of these is provided with the pintle receiving openings40.

Coming back to Figure 5, it will be seen that the uppermost link L1 isdisposed immediately below the lug D1 of the door plate DP with itsopening 30 in registry with the pintle opening 15 of the lug whereby thetwo elements are connected by the pintle bolt 45'. Immediately below thelink L1 is disposed the similar link L2, the right-hand end of whichrests upon the lug 11 of the jamb plate JP and the respective openings30 and 1.5 are in registry and receive the pintle pin 46. Theintermediate boss portions of the links L1 and L; are pivotallyconnected by means of the pin 47.

Below the link L2 there is disposed the link L which conforms to theshape of the one shown in Figure but is disposed in an invertedposition. The narrowed portion of the link L3 rests upon the lug D2 ofthe door leaf or plate and is pivotally connected thereto by means ofthe pintle pin 48. The intermediate lug 36 of the link Ls receives a pin49 which extends upwardly into the opening 34 of the left-hand endportion of the link L2. Below the link L3 and extending in the oppositedirection therefrom is the link L4 which has its narrowed end portionpositioned below the jamb jug J2 and pivotally connected thereto bymeans of the pin 50. The righthand end of the link L3 and the left-handend of the link L4 are pivotally connected by means of the elongatedpintle pin 51.

Below the link L4 the pattern of linkages is substantially repeated, thelink L11 (corresponding to the link L1 at the top of the system) ispivotally connected at its left-hand end to the door plate lug D3 bymeans of the pintle bolt 52 and at the right-hand end being pivotallyconnected with the intermediate portion of the superposed link L4 bymeans of the pin 53. The next link L22 is pivoted by means of the pintlebolt 55 to the jamb lug J3 and is also pivoted at its intermediate pointto the central portion of the link 11 as by means of the pin 56.

The left-hand end of the link L22 is pivotally connected with theintermediate portion of the link L33 as by means of the pin 57.

In a similar fashion to the corresponding element L3 of the upper seriesof links, the link L33 is pivotally connected by means of the pin 58 tothe lug D4 of the door plate and has its intermediate portion pivotallyconnected by means of the pin 59 to the left-hand end portion of thelink L44 next below. The right-hand cut-away end of the link L44 ispivotally' connected by means of the pin 60 to the jamb lug J4. Thiscompletes the connection of the links with the jamb and door leaves.

For the purpose of binding the linkage system together and establishingthe proper continuity of transfer of compression forces throughout thesystem, there is provided a binding cleat or bar B which is illustratedin elemental form in Figure 11 of the drawings. The upper and lower endsof the bar or strap B are bent at right angles to form the lugs or earsB1 and B2, which are pierced with pintle receiving openings 61. As mostclearly shown in Figures 4 and 6 of the drawings, the bar B is fittedaround the linkage system so as to clamp the superposed links togetherand occupies a position in which the upper lug B1 of the bar overliesthe right-hand end of the link L1 and is pivotally connected therewithby means of the pintle bolt 62. The lower ear or lug B2 of theconnecting or clamping bar underlies the intermediate portion of thelowermost link L44 and is pivotal ly connected thereto by means of thepin 64.

It is believed that the position of the various elements in wide opencondition as shown in Figure 5 will be clearly understood, and referenceis now made to Figures 3, 4, and 6 of the drawings in which the partsare illustrated as occupying the door-closed positions. In moving tothis position, the parts pass through the position shown in solid linesin Figure 2 of the drawings and it is interesting to note theparallelogram configuration of the linkages in this intermediate orhalf-open position. The links L1 and L11 which extend from the doorplate lugs D1 and D3 cross the links L2 and L22 which extend from theinner lug J1 of the jamb and are pivoted at the intermediate points 47and 56 respectively. The links L1 and L11 extending from the door platelugs and the links L2 and L22 extending from the inner jamb plate lugsare prolonged to a point where their outer ends may be pivotallyconnected to the intermediate portions of the links L3 and L33 on theone hand and the links L4 and L44 on the other hand. The links L3 andL33 extending from the lugs D2 and D4 of the door plate are prolongeduntil their outer ends register with the outer ends of the links L4 andL44 respectively which extend from the iamb lugs J2 and J4. This extremeouter meeting point is occupied by the superposed pivots 51 and 59. Theposition of the clamp bar B is clearly shown in Figure 2 as occupying aposition intermediate the ends of the link L4 and at the terminals oflinks L1 and L11.

In passing from the half-open position indicated in Figure 2 to theclosed position indicated in Figures 3, 4, and 6, the successive hrizontal links are stacked sub stantially in a plane marking the line ofseparation between the door and the jamb as shown in Figure l of thedrawings, this stacking of the links being slightly narrower in lateralextent than the stacking arrangement shown in Figure 5 where the door isin opened position, but all of the links, bearing one upon the other,adequately sustain the weight of the door, in all positions of thelatter. As most clearly shown in Figures 3 and 4 the clamp bar or cleatB moves into the plane of the jamb plate JP and occupies the cut-outportion or slot S formed in the plate.

Both the clamp bar B and the extension of the links L3, L4, L33 and L44to the apexes represented by the pintles 51 and 59, contribute towardmaking the hinge capable of carrying heavy door loads satisfactorily.Most hinges of this type in the prior art omit the extenmenses:

si ons' represented by the outer endsof links -L3-and L4 and the pintle51, and the corresponding elements of the lower portion of the hinge,and terminate the outermost links at the intermediate pointsrepresented'by the pintles. 49 and 62 and in such arrangements the shearstrength is very small and is so unsatisfactory that it renders thehinge almost useless for practical purposes. In the absence of the apexhinge pintles, what shear strength there is depends upon the pintlepins'and the binding of the members, which obviously soon wears thehinge out.

With the hinge points 51 and 59 provided by the prolongation of thelinks or arms L3, L4, L33 and L44 the links or arms act as miniaturebeams, which give a very high readily calculable strength. The stresseson the various elements have been carefully Worked out by the applicantand are represented by the small arrows applied to Figure 3 whichindicate the places where the members of the hinge bear one upon theother. Two arrows indicate twice as much bearing stressas one arrow andfour arrows indicate four times as much bearing stress as one arrow.Thus, if one hinge link or arm (L3, L4, L33 and L44) has one unit ofbearing stress on each end, it has two units of bearing stress inthecenter of the respective links, but in the opposite direction. Thismeans that these links will be taking bending loads, i. e. loads whichwould produce bending of the links.- Links L1, L2, L11 and L22 each havetwo units of bearing stress at each end of the links, and four units inthe opposite direction at the centers of the respective links.Therefore, these links also are balanced and under bending'stress. Onthe mounting plates JP and DP there are tWo units of bearing stress attwo of the ears on the respective plates in one direction and one unitof stress at two of the ears in the opposite direction, leaving twounits of stress as the actual shear value from the door to-the jamb orvice versa for the bearing and bending stresses recited above.

The above mentioned calculable strength of the hinge with the additionalapex pintle point is madepossible by the continuity obtained by the useofthe binding cleat or bar B. In fully open or fully closed position allof the links occupy the same plane and bear directly upon one anotherthrough a substantial portion of their lengths. However, when in anintermediate position it is necessary to use the binding cleat B toclose the circuit so to speak, thebinding cleat enclosing the twocomplete sets of linkages and exerting clamping contact over the link L1and under the link L44.

In developing the present invention, it was found that the hinge couldbe strengthened and tension on some of the pintle pins removed byeliminating filler blocks in association with the links and making thelinks L3, L4,

L33 and L44 wider than links L1, L2, L11 and L22 and then notching out acorner of the widest links as shown in the detail view in FigurelO. Thepintle pins, in this construction, do not carry any shear load due tothe weight of the door and their principal functon is to guide the doorduring the folding and unfolding of the linkage systems and to preventthe door from falling away from its erect position. There is no tensionon the pintle pins, and they may therefore be merely press-fitted intoone of the two members which are connected by each pin.

In this connection it is well to mention that the screw pintles 45, 62,52, and 55 may be replaced by drive pins such as illustrated in Figures14 and 15 of the drawings where the pins P are provided through aportion of their length with an annular series of grooves '70 which areso cut into the periphery of the pin P as to raise a pair of cuttingedges 71 alongside of each groove, which cutting edges embed themselvesin the walls of the opening into which they are driven and rigidlyretain the pin within said openings. The positioning and functioning ofthese pins are clearly shown in Figure 13 of the drawings where two ofthe drive pins P are installed at 6211 and 49a in the assembly insubstitution for the earlier described screw pins and plate drive 6pins. It Will be seen how the burrs provided by the cutting edges 71embed themselves in the walls of the openings 61 in the bar lug B1 and40 of link L3, while the .smooth portions of the respective pins 62a and49a are rotatably received within the openings 30 of the links L1 andL2.

In Figure 12 of the drawings there is illustrated a small bullet-shapedplug 75 which is preferably made of rubber or some similar resilientplastic material and provided with a nose 76 and the similarly shapedrecess 77 in the other end thereof. One of these small rubber springelements is inserted in each one of the sockets 19, 20, 21, and 22 ofthe hinge leaves JP and DP and it will be readily seen, from aninspection of Figure 5, how the projecting ends of these spring elementsare contacted and compressed by the links L3, L4, L33 and L34 when thedoor is in the wide open position. These springs being under tension,they serve to urge the linkages away from dead center position when thedoor starts to move toward closed position. The hollowed end portions 77of the spring plug 75 provides for the necessary displacement of thematerial in the forward end of the plug when it is under compression bycontact with the links. The rubber or other material of which the springis composed is therefor largely stressed in shear and should maintainits resiliency for a great length of time. If desired, a small helicalspring made of metal might be substituted for the rubber plug 75.

In the manufacture of the hinges the plates or leaves JP and DP and thebar B should be steel stampings of a most inexpensive composition. Thelinks shown in Figures 9 and 10 may also be made of steel and plated,but they should preferably be made from extruded brass since in thisform the cost of manufacture'is relatively small.

The process of installation of the hinges is is also quite simple whenpursued according to the following sequence of operations. Referring toFigure 3 of the drawings it is suggested that the parts be assembled inthe following order. With the door plate or leafDP as a basis, the linkL33 may be connected with the lug D4, the link 22 next applied and thenthe link '11, whereupon the screw bolt 52 is inserted to connect thelastnamed link with the lug D3. Then link L4. is applied to theassemblage. The screw lug 55 may then be applied to connect the link L22to the lug J's. Next the links L3, L2 and L1 are superposed in thestated order and the screw pintle 45 employed to attach the link Li'tothe lug D1. Then the link 1.44 is inserted and the bar B applied to theend links L1 and L44 and pinned into position.

In Figures 1622 inclusive of the drawings there is illustrated anotherembodiment of the invention in which are employed fiat horizontallydisposed links connecting the jamb and closure leaves of the hingeassembly, these plates being arranged to be stacked in a common plane inthe fully closed and fully opened positions of the mechanism, just as inthe case of the previously described embodiment. However, certaindifferences in details of thedtwo embodiments will appear as thedescription procee s.

In these figures, the jamb or support member of the combination isdesignated by the reference character M and the swinging door or otherclosure is designated N. The respective abutting edge portions of thesetwo members are provided with shallow recesses for the reception andcomplete concealment of the hinge assembly when the door is in closedposition. The hinge proper comprises 7 bent outwardly from anintermediate portion of the plate.

The lugs comprising the first's'eries' are designated M1,

M3, M5, M7 while those of the second series are indicated by thereference characters M3, M4, Ms, Ma.

The door plate or leaf NP is similarly provided with two series of lugsN1, N3, N5, N7, N2, N4, N6, N8 occupying corresponding positions on thedoor leaf.

The connecting links which are pivotally secured to the lugs and also toadjacent links are of two types, one being indicated generically by thenumeral 100 in Figure 21 and the other by the numeral 101 in Figure 22.The links 100 are of full width for somewhat more than half of theirlength and are narrowed for a portion of their extent as at 102.Intermediate and end pintle-receiving openings 104 are provided in thelink 100. The link 101 is provided with an intermediate angular portion105 which serves to offset an end portion of the link from the remainderthereof. This link is somewhat narrower than the widest portion of thelink 1%, the width of the greater portion of the link correspondingapproximately to that of the narrower part 102 of the link 1051. Thelink 101 is provided with rounded end and intermediate portions 166through which pintle-receiving openings 107 are made.

Referring now to Figures 19 and 20, the arrangement and connections ofthe various linkages will be described. The first link, counting fromthe top of the assembly, is of the generic type 101 and is designatedR1, the left-hand end of the link being pivotally connected with the earN1 of the door plate NP by means of a pintle or rivet a The oppositeoifset end of this particular arm R1 is not attached, and could bedispensed with if desired, but is shown as used intact since it isprobably more economical to make all of the links of each type in auniform manner regardless of their particular position in the assembly.

The intermediate portion of the link R1 is pivoted by means of the pinor rivet b to the intermediate portion of the next lower link R2. Oneend of the link R2, that is the straight or non-offset end, is pivotallysecured to the ear M by means of the pin c and the remote or oifset endof the link R is pivoted by means of the rivet or pin d to theintermediate portion of the straight link R of the type genericallyrepresented in Figure 21 at 100. One end of the link R is pivoted to thedoor plate ear N2 by means of the pin e1 and this straight link or barR3 has its opposite end pivoted to the end of the similar matingstraight bar R4 by means of the pin f1. The opposite end of the link R4is pivotally connected by means of the pin g to the ear M2. Theintermediate portion of the straight bar R4 is pivotally connected bymeans of the pin in to the offset end of the next link R11, and theseconnections complete one cycle or series of connections, the remaininglinks being pivotally attached to each other and to the hinge plates orleaves in exactly the same way throughout each of four series. The linksor bars themselves are designated R11, R12, R13, R14 R21, R22, R23, R24;and R31, R32, R33, R34, and the pins or rivets connecting the variouslinkages are designated az-hz; az-hs; and (14-3 4, for the remainder ofthe series of linkages.

From an inspection of Figure 16 particularly the arrangement of theparts in the intermediate or half opened position, it will be seen howthe linkages assume the parallelogram or lazy-tong configuration inexactly the same manner as the embodiment of the invention firstdescribed. The straight bars R3, R4, R13, R14, R23, R24, R33, R34,pivotally connected at f1, f2, f3, f4, provide the outermost linkageswhich meet at the apex represented by the rivets of the series f1-f4.The position of the intermediate bars or links R1, R2 and similarlydesignated units, is also shown in Figure 16 as well as the intermediatepivot points b1, d and hi. The pivotal connections of the variouslinkages with the ears on both the jamb plate and the door plate areshown at a1, 01, c1, and g1.

For urging the stack of linkages away from the wide open dead-centerposition shown in Figure 2 of the drawings, resilient means are providedincluding the arcuate elongated spring elements 111). The bowedintermediate portions of these springs are secured to the plates MP andNP as by means of the screws 111 which may also serve, together with thescrews 112, to secure the plates to the jamb and door edges within therecesses provided therefor. It will be readily seen that when thelinkages are in the dead-center position shown in Figure 20 the edges ofthe springs will be contacted by the bars R3R33 and R4R34 and will beplaced under stress and when the door is started toward closed position,the springs will serve to urge the linkages outward and break anydead-center detention which might occur.

It should be borne in mind continually that the broad principles of thepresent invention may be applied to hinge assemblies for the closures ofboxes, chests, or other containers, where the closures may at timesoccupy horizontal planes and may swing in vertical planes. However, forthe sake of brevity and clearness of terminology, the closure will bereferred to in the claims as a door, and the relatively fixed body towhich it is hinged will be designated a jamb.

For certain purposes a hinge might be made up of linkages of one seriesor cycle only, for example, links L1-L4 inclusive.

Various changes and modifications may be made in the embodimentsillustrated and described without departing from the scope of theinvention as determined by the subjoined claims.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. In a concealed butt hinge assembly for doors and other closures ofthe class described, in combination, a jamb leaf and a door leaf adaptedto move about a pivot axis exterior of the closure through an angle ofapproximately from a door-closed position, in which they are disposed inclose parallel relationship, to a door-open position, in which theleaves are in substantial alignment; at least one pair of verticallystaggered lugs projecting from each of said leaves, at least one firstpair of links pivotally connected together substantially at theirrespective midpoints and having two opposed ends, one on each link,pivotally connected to the innermost lug of each of said pairs, at leastone second pair of links having their adjacent ends pivotally connectedtogether and having their remote ends pivotally connected to theoutermost lug of each of said pairs, one of said second pair of linksbeing pivotally connected at an intermediate point to a free end of oneof said first pair of links, said links being stacked vertically andhaving their upper and lower surfaces at least in the region of thepivotal connections in bearing contact with the next adjacent link, saidlinks being all of substantially the same length, whereby the bearingforces applied to the hinge assembly of the door when supported by thejamb longitudinally of the hinge assembly are substantially entirelysustained by stress on the links and lugs with substantially no bendingor shearing stress on the pivotal connections, the axes of pivotalconnection lying within a common vertical plans when the door is both infully opened and fully closed positions.

2. The hinge assembly of claim 1 including a clamping bar independentfrom said leaves and embracing all of said links, said bar beingpivotally connected to and bearing upon the free end of the other ofsaid first pair of links and that link in the assembly most remote fromsaid other of said first pair of links whereby there is obtained abalance circuit of stress throughout the entire inkage system.

3. The hinge assembly of claim 1 in which the stacking plane of thelinks in both door-open and door-closed positions is closely adjacentthe plane of the door and jamb leaves, whereby a shallow recess in thedoor edge and/or the jamb edge will accommodate and conceal the hinge;and in which when the door is fully open the pivotal axes of said secondpair of links are aligned in dead center position, there being providedupon at least one of said leaves inwardly of an outer lug and inhorizontal alignment with one of the links of said second pair a springprojection which is contacted and placed under resilient stress by saidlast mentioned link when the door is in fully open position to breaksaid pair of links from its dead center position and urge the linkagetoward door-closed position.

4. The hinge assembly of claim 1 in which said lugs are provided withaligned vertical apertures at the points of pivotal connection and apintle pin is tightly received by one of said apertures and looselyreceived by the other to thereby provide said pivotal connection.

5. The hinge assembly as in claim 1 in which said links compriselongitudinal elements having appreciable thickness in the dimensiontransverse to and co-planar with the longitudinal axis of the elements,and having the same general horizontal cross-sectional configuration,said elements being laterally enlarged at at least the ends andintermediate portions thereof to provide bosses, the upper and lowersurfaces of which are adapted for bearing contact with correspondingsurfaces of adjacent links.

6. The hinge assembly set forth in claim 1 in which certain of the linksare bent between their intermediate and end pivot points to provide anoffset portion in order to avoid conflict with the leaf lugs.

7. The hinge assembly as set forth in claim 3 in which the springprojection comprises a compressible lug of rubber-like material set inan opening in the leaf and projecting therefrom.

8. The hinge assembly as set forth in claim 3 in which the springprojection comprises an elongated strip of thin spring metal securedmedially to one of said leaves, extending longitudinally of theassembly, and having its lateral edges curled outwardly to project intothe plane of the stacked links.

9. In a concealed butt hinge assembly for doors or other closures of theclass described, in combination, a jamb leaf and door leaf adapted tomove about a pivot axis exterior of the closure through an angle ofapproximately 180 from a door-closed position, in which they aredisposed in close parallel relationship, to a dooropen position, inwhich the leaves are in substantial alignment; two transversely spacedseries of lugs projecting from each of said leaves, one of said seriesadjacent the pivot edge of each leaf and the other remote from saidedge; a series of links vertically stacked in bearing contact each withthe next adjacent link; the links being all of substantially the samelength and arranged in pairs of adjacent similarly shaped and positionedlinks; a first pair of said links each having one of its ends pivotallypinned to a lug in the series further from the edge of the door leaf andthe jamb leaf respectively which is adjacent the pivot axis of theclosure and having its other end pivotally connected to the oppositeoverlapping end of its mating contacting link; a second pair of saidlinks each having one of its ends pivotally connected to a lug in theseries nearer the pivot edge of the door leaf and the jamb leafrespectively, and its intermediate point pivotally connected to theintermediate point of its mating link; the intermediate point of atleast one of the links of said first named pair being pivotallyconnected to an end of the one of the links of said second named pairnext adjacent thereto; the bearing forces applied to the hinge assemblyby the door when supported by the jamb longitudinally of the hingeassembly being substantially entirely sustained by stresses on the linksand lugs with substantially no bending or shearing stress on the pivotalconnections, each link comprising a simple lever and the stresses oneach of the links being balanced symmetrically thereof; and a clamp barindependent from said leaves embracing the series of links and bearingupon and pivotally pinned at its respective ends to the outer sides ofthe outermost links of the series, in order to complete the balancedcircuit of stresses throughout the entire linkage system.

10. The hinge assembly as set forth in claim 9 in which no two lugs onboth of the leaves taken together are in transverse alignment and inwhich certain of the links have an end portion partially cut away toprovide space for certain of the lugs, whereby the bearing contactbetween those links and the next adjacent ones may be maintained.

11. The hinge assembly as set forth in claim 9 in which the pattern oflinkage construction and arrangement is repeated serially longitudinallyof the assembly, and a single clamp bar is employed, said bar embracingand contacting the uppermost link of the first series and the lowermostlink of the last series.

References Cited in the file of this patent UNITED STATES PATENTS373,611 Scheidemann Nov. 22, 1887 414,461 Towson Nov. 5, 1889 465,707Williamson Dec. 22, 1891 818,435 Gonyo Apr. 24, 1906 879,067 Rodman Feb.11, 1908 1,011,512 Soss Dec. 12, 1911 1,030,936 Soss July 2, 19121,211,366 Fisher Jan. 2, 1917 2,021,702 Soss Nov. 19, 1935 2,189,048Underhill Feb. 6, 1940 FOREIGN PATENTS 828,436 France May 18, 1938

